The invention relates to a solenoid valve for metering a fluid into an intake tract of an engine. The invention further relates to a method for producing a series of solenoid valves which differ with regard to the maximum flow rate thereof.
The specified solenoid valve is particularly to be used as a metering valve for a gaseous medium, preferably for a gaseous fuel. Furthermore, the valve's use in large engines is of primary importance. The mass flow rates up to 3000 kg/h typically required for large engines require relatively large opening cross-sections of the metering valves used therein. At the same time, the metering valves must be able to meter small amounts of fluid in low load ranges. This ability requires high switching dynamics. In order to be able to realize said high switching dynamics, it is necessary to keep the switching forces as low as possible. As a rule, pressure-compensated valves are therefore used.
A pressure-compensated, electromagnetically actuated valve for use in large engines is based, by way of example, on the American patent specification U.S. Pat. No. 8,272,399 B2. Said valve comprises a solenoid assembly, a stroke-movable armature that interacts with the solenoid assembly and a stroke-movable valve disc which is connected to the armature and is used for opening and closing a plurality of slit-like through-flow apertures in a valve plate. The stroke-movable valve disc likewise comprises slit-like through-flow apertures, between which a sealing surface remains that can be brought into register with the through-flow apertures of the valve plate in order to seal off a valve chamber from a pressure chamber located outside of the valve. The pressure chamber located outside of the valve is connected via a central pressure compensation hole, which passes through the valve plate and the valve disc, to a pressure compensation chamber; thus enabling the same pressure to prevail in the pressure compensation chamber and in the pressure chamber, which pressure generates a compressive force acting on the armature in the closing direction and a compressive force acting on the valve disc in the opening direction. The pressure prevailing in the valve chamber, which generates a compressive force on the valve disc in the closing direction and a compressive force on the armature in the opening direction, is likewise applied to the armature and the valve disc. The surfaces subjected to pressure are selected such that the movable components, namely the armature and the valve disc are substantially pressure compensated in the closed position. The pressure balance results in the required switching forces being significantly reduced.
Such pressure-compensated valves have however the disadvantage that, as the flow cross-sections of the through-flow apertures provided in the valve plate change, the surfaces relevant for the pressure balance also change. A change in the flow cross-sections can, for example, be due to customer specific requirements. As a result, the movable components and/or the solenoid assembly have to be redesigned and readjusted to one another in order to reestablish the pressure balance.